I have multiplus ii 48/5000-70, managed by VenusOS (Raspberry), attached to 2 JKBms managed batteries in parallel 16kw each. Charge/Discharge is controlled via acsetgridpoint from NodeRed automation
As I understand, inverter should provide a peak charging of batteries of 4000w, and yet I am observing this very underperforming situation on every charge.
How fast a battery charges can be affected by alot of things.
Inverter is programmed internally to use all charge amps?
Your grid set point - you go that covered and above 25A input current limit + whatever cover loads on output if there are any?
Charge voltage set point also matters. Low or closer to battery voltage and it doesnât shunt in.
Temperature of batteries and inverter sometimes -although that usually without battery life is not an issue unless the bms is clever. Its requesting 200A that doesnât mean its letting it in
Also sometimes setting keep batteries charged works better for some reason. I havenât investigated/looked into behaviour whether that shifts CVL or not with a JK.
Sometimes i have found actually letting the inverter do what it does with no bms control actually works better
Your grid set point - you go that covered and above 25A input current limit + whatever cover loads on output if there are any?
Sorry not sure I am following
Charge voltage set point also matters. Low or closer to battery voltage and it doesnât shunt in.
Temperature of batteries and inverter sometimes -although that usually without battery life is not an issue unless the bms is clever. Its requesting 200A that doesnât mean its letting it in
Batteries temp were stable at 16C
Also sometimes setting keep batteries charged works better for some reason. I havenât investigated/looked into behaviour whether that shifts CVL or not with a JK.
Sometimes i have found actually letting the inverter do what it does with no bms control actually works better
In cooler temps I couldnât keep a 5kVA at full power indefinitely. Somewhere near 30 minutes, much less in warmer temps, it would derate down to 2800-3000W.
Not saying they arenât capable. But that programming has alot to do with it as well.
Ok. So higher than ambient which means the inverter could be quite warm. I obviously dont know all the ins and out of the installation like air movement and clearance and heat exhaustion in the room it is in. So you are the better one to judge.
Rhis is what i have found to be the time around for heat âsaturationâ as well. Unless additional methods for air movement are implemented.
If you have managed discharge to grid at 25Amps at mains voltage then it is not the input current limit. (Programmable on the inverter and possibly overrriden by remote). Basic math is 24x230v is 5750watts.
Was just in the Garage where the inverter is situated (ambient temps around 12C), and while I was there fan kicked in and temperature led began to blink
All of this in pretty low temps, I am getting pretty concerned now what will happen during the summer when ambient temps can reach 40C
I have 2 Sunlu fans coming in which will be placed for additional airflow, but is this a normal behaviour of these units or should I be concerned warranty wise?
The moral of the story is not to size a system so it has to run at 100% continuously. Nothing is efficient at 100%.
The warmer the climate, the greater the headroom you will need.
I would consider a larger inverter like an 8000 or think about paralleling another, alternatively restrict the charge current.
You havenât shown photos of your installation, placing warm systems beneath it isnât recommended. It is important to keep good clearances around the system for airflow.
And in the case above I have reached the point of thermals kicking in after a minute of maximum output? All of this in the ambient temperature of about 12C.
Limits I am observing (unless they are not temp related) corresponds to about 50C on those graphs. I have added now a temperature sensor on the top exaust vent of Multiplus, so should be able to have a better grasp of whats happening temp wise.
The installation while is not ideal, does provide roughly 10 cm around and 2cm on the back. (yes, there are batteries below but they do not alter the ambient temperature too much, maybe couple of degrees) https://s6.imgcdn.dev/YGUjfC.jpg
I have a couple systems whose entire job is to charge and feedback strategically with no solar.
Donât do max power but look at the inverter datasheet - use their load at peak efficiency - tailor the charge and discharge for that. Not using wattage but amps moving on the dc bus- so the power in and out has a slope depending on battery voltage. Peak may be slightly variable depending on dc set up and the bms used actually matters as well. (Cloured me surpised -some sarcasm intended)
inefficient means heat. Heat means derating.
Nice point.
A physical check may be in order - check if the fans in the unit are actually working
I am assuming there is only one fan, if thats the case then its working.
Digging down, there is a thermal warning kicking in as soon as load comes in. I have tried couple of times to forse discharge and these are results
Just to be clear, right now we are not talking about trying to get a peak performance for long period of times, but degrading with temperature alert coming in after a minute or so
No fan assistance as far as i remember (and tbh it does kick in full speed straight away). Yes, the whole charging/discharging is done via setting SetPoint through NodeRed.
Have not tested the keep-charged yet, but for what its worth, I am getting thermals kicking in on the DISCHARGE operation. Right now I am unable to sustain a kettle boiling without triggering thermal warning.
Added additional fan blowing from below with no result whatsoever.
Edit just realized what could be causing the confusion, on my âPower Controlâ graph values are inverted, so positive=discharging and negative=charging)
The Multiplus 48/5000/70A is rated at 70A for battery charging, which into 53V is 3.7kW. Youâre seeing 2.64kW continuous which is 50A, so about 70% of the rated value.
That stacks up with my experience of a Quattro 48/10000/140 which is specified as 140A for battery charging, but actually only delivers 100A after a couple of hours â no thermal warning, just throttles the current backâŚ
right now I am being throttled after 5 minutes but yeah, I was already gutted when âdiscoveredâ that 5000 doesnât mean 5kw in battery (first install etc), now discovering that it doesnât mean 4kw either XD.
Also, my firmware version is pretty old (498), and there have been multiple improvements over the charging limit since then by the look of it. Once the termal thing is solved will probably try to update it and see if the charging improves.
Meanwhile, raised the support request to the Victron through reseller regarding the temperature warnings being fired off, will see what they say.
but yeah, I was already gutted when âdiscoveredâ that 5000 doesnât mean 5kw in battery (first install etc), now discovering that it doesnât mean 4kw either XD.